Internal combustion engine comprising an electromagnetic actuator which is situated on a cylinder head

ABSTRACT

An internal combustion engine includes an electromagnetic actuator for operating a gas exchange valve, this actuator being situated on a cylinder head. The actuator includes a switchable electromagnet which is situated between two armatures. The armatures are axially set apart on a common armature shaft. A cavity is configured in the cylinder head, in which the actuator armature on the cylinder head side is at least partially accommodated, and the electromagnet at least partially delimits the cavity on the actuator side. This results in a compact internal combustion engine.

BACKGROUND AND SUMMARY OF THE INVENTION

This invention concerns an internal combustion engine with anelectromagnetic actuating mechanism arranged on a cylinder head.

Such an actuating mechanism is known from German patent document DE 19712 669 A1. Moreover, an electromagnet is arranged between two anchors inan axially spaced construction on the valve tappet. A coil core of theelectromagnet has one or more pole surfaces on the respective sidesfacing the anchors. When the electromagnet is subjected to current, aforce acting upon the respective closest anchor predominates. Inparticular, an alternating motion of the actuating mechanism andconsequently an opening and closing of the gas exchange valve coupledwith it can be realized in the interaction with the dynamics of theactuating mechanism through an alternating interruption and subjectionto the current in the exciter circuit.

The problem in any case with the arrangement of such actuators oncylinder heads is the overall height. When actuating mechanisms arebuilt too high, space problems can arise in the motor area. Inparticular, problems can arise during motor vehicle assembly and whenpositioning the motor in the motor space.

For this reason, it is one object of the present invention to specify aninternal combustion engine that is compactly constructed to a particularmeasurement.

This object is reached by the measures specified in claim 1.

Moreover, basic to the invention is the construction of a hollow spacein the cylinder head that accommodates a part of the actuatingmechanism. This component is mainly, at least in part, the cylinder headside anchor of the actuator unit, whereby the electromagnet lyingbetween the anchors at least partially delimits the hollow spacementioned on the actuator side. Through the formation of the hollowspace mentioned above, and by shifting the actuator elements into thehollow space that then becomes possible, the height can be reducedsignificantly in the direction of the cylinder, which leads to a morecompact internal combustion engine overall, especially taking intoaccount the large number of actuator mechanisms to be installed.

Above and beyond this, favorable heat extraction can be attained bydirectly positioning the electromagnet on the cylinder head so that theactuator can easily be cooled.

In accordance with an advantageous design, the anchor shaft is mountedin the electromagnet itself. In this way, it is important to fix theelectromagnet into a position relative to the cylinder head.

The anchor shaft of the actuating mechanism can be indirectly ordirectly coupled with the valve shaft of the valve, for example, byinterposing a valve play compensation element.

In order to utilize the hollow space even better, a first spring (valvespring) should be installed according to an especially advantageousdesign of the invention. This valve spring can prestress the valve intoan end position, for example the closed position. The valve spring ismoreover advantageously braced on the valve shaft, on the one hand, andon the cylinder head, on the other. This makes it possible to installthe valve in a simple manner.

A second spring (actuator spring) can be incorporated into the actuatingmechanism and can be installed far from the cylinder head in relation tothe electromagnet. The simple construction of this design is furtheredif this actuator unit spring is braced directly against the anchor farfrom the cylinder head. Through a screw device by means of which theactuator spring can be held above a spring seat, an adjustment of theactuator unit, especially of the two anchor plates, can moreover beconducted with respect to its position toward the electromagnet. Theelectromagnet can include a coil core with one or more pole surfaces asis known, for example, from German patent document DE 197 12 669 A1.

The present invention will be explained in greater detail below on thebasis of a design and with reference to the appended drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional representation of a unit formed by twoelectromagnetic valves which are arranged on a cylinder head, and

FIG. 2 is a sectional representation of an actuating mechanismconstructed in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION

In FIG. 1, an assembled unit is represented in cross-section, whichbasically consists of two electromagnetically activated gas valvesarranged on a cylinder head.

The structure of an electromagnetic actuating mechanism for such a gasvalve is first described on the basis of FIG. 2.

The actuator 10 includes an electromagnet 12 that is only represented asa unit. The electromagnet 12 can encompass one or more pole surfaces onthe sides facing the respective anchors as one or more coils. Twobearings 15 are constructed in the electromagnet coaxially with acentral bore hole on both end regions that hold an anchor shaft 14flexibly guided in an axial direction. Two anchor plates 16 and 18 arespaced at a distance from each other axially on the anchor shaft. Theyare located on opposite sides of the electromagnet 12. The front anchorplate 16 is constructed smaller than anchor plate 18. In a zero pointposition of the anchors that are the same distance from theelectromagnet 12, this asymmetry is important for oscillations of theactuating mechanisms in the starting position of the combustion engineas the pressure is greater on the upper anchor plate 18 than the on thelower anchor plate 16. The distance between the two anchor plates 16 and18 is greater than the thickness of the electromagnet 12 so that analternating motion is guaranteed in a specified region.

The electromagnet 12 is accommodated in a housing 20 such that, togetherwith the housing 20, it basically delimits the actuating mechanism onthe side of the small anchor plate 16. In this way, the anchor plate 16stands together with the anchor shaft 14 projecting on this side overthe volume bounded by the electromagnet 12 and the housing 20.

In the upper region of the housing 20 represented in FIG. 2, a bore holeoriented coaxially toward the bore hole in the electromagnet 12 isconstructed with an internal thread into which a screw device 26 can berotated. At the same time, the screw device 26 forms a spring seat foran actuating mechanism spring 22 that is first braced against thisspring seat and secondly against a valve seat arranged directly onanchor plate 18. The actuator spring 22 serves to prestress the gasexchange valve in the open position and is compressed in the designpresently represented. The screw in device 26 includes above and beyondthis a central, stepped bore hole into which a path sensor 28 (presentlynot represented in greater detail) is inserted. The path sensor 28 onceagain includes a central borehole arranged coaxially toward the cylinderborehole through which a prolongation of the anchor shaft 14 projects.

Subjecting the electromagnet 12 to current takes place through feederlines of which only one is presently represented with reference number30.

A so-called oil gallery is designated with reference number 23. This isa supply line for lubricating oil that terminates in the region of theupper anchor plate 18 and assures minimal lubrication through adrop-by-drop administration of lubricating oil.

In accordance with FIG. 1, a cylinder head 50 of the internal combustionengine is constructed with a recess (hollow space) 58 in the region ofeach valve in which the actuator element (anchor plate 16 and anchorshaft 14) is accommodated, projecting beyond the housing 20 andelectromagnet 12. Moreover, the valve 52 that is mounted in the cylinderhead stands opposite the actuating mechanism into the hollow space 58.

A spring seat 56 is mounted on the upper end of the valve 52 againstwhich additional springs, namely the valve springs 54, are braced. Thevalve spring 54 is on the other hand braced against a spring seatdirectly on the cylinder head and prestresses the valve in its closeddirection. A valve play compensation element not represented in greaterdetail is provided on the upper end of the valve.

During assembly, the anchor plate 16 together with the anchor shaft 14is introduced into the hollow space 58 so that the front end of theanchor shaft comes to lie on the valve shaft of the gas exchange valvearranged therein by interposition of the valve play compensationelement. In this way, there exists a coupling between the actuatingmechanism 10 and the valve 52. An anchor position is reached through asuitable dimensioning and arrangement of springs 22 and 54 or thecorresponding spring seats, in which the electromagnet comes to lieapproximately between the two anchor plates 16 and 18 (not presentlyrepresented). This represents the resting position. Through the present,asymmetrical choice of the two anchor plates 16 and 18, an initialdisplacement can be attained during start-up by subjecting theelectromagnet to current so that ultimately an alternating oscillationof the spring aggregate system consists of anchor, valve and valvespring with subsequent, suitable alternate presence and absence ofcurrent. Moreover, the lower anchor plate 16 alternates in the hollowspace. Both anchors 16, 18 can be held in their respective end positionsnear the electromagnet through continuous administration of current.

The hollow space is predominantly bounded by the electromagnet on theactuator unit side. By accommodating valve and actuator unit elements inthe hollow space 58, an especially concisely built unit consisting ofthe cylinder head and actuating mechanisms can be achieved, which is thegoal of the present invention.

In addition to this, the electromagnet 12 lies directly on the cylinderhead, at least in its edge regions, which is always well cooled. Throughthis optimal thermal coupling, good heat dissipation of the heatgenerated in the in the actuating mechanism is achieved, especially theelectromagnet 12 itself, without having to take special cooling measuresfor the actuating mechanism.

1. An internal combustion engine with an electromagnetic actuatingmechanism arranged on a cylinder head for operating a gas exchangevalve, the actuating mechanism comprising: a switchable electromagnet,and two movable anchors arranged axially at a distance on a commonanchor shaft on which the switchable electromagnet is mounted, wherein ahollow space is constructed in the cylinder head and a cylinder sideanchor of the actuating mechanism is at least partially accommodated inthe hollow space, wherein the electromagnet at least partially delimitsthe hollow space, and wherein the electromagnet lies at least in partdirectly on the cylinder head and is thermally coupled with the cylinderhead.
 2. The internal combustion engine according to claim 1, whereinthe anchor shaft is mounted in the electromagnet.
 3. The internalcombustion engine according to claim 2, wherein a penetrating bearing isor at least two bearings are provided.
 4. The internal combustion engineaccording to claim 1, wherein the anchor shaft is indirectly or directlycoupled with a valve shaft of the valve, and wherein the valve ismounted in the cylinder head.
 5. The internal combustion engineaccording to claim 4, wherein a valve play compensation element isprovided between the anchor shaft and the valve shaft.
 6. The internalcombustion engine according to claim 4, wherein a first spring thatprestresses the valve into an end position is provided in the hollowspace.
 7. The internal combustion engine according to claim 6, whereinthe first spring prestresses the valve in its closed position.
 8. Theinternal combustion engine according to claim 6, wherein the firstspring is supported on both the valve shaft and on the cylinder head. 9.The internal combustion engine according to claim 6, wherein a secondspring is arranged at a distance from the cylinder head in relation tothe electromagnet.
 10. The internal combustion engine according to claim9, wherein the second spring is braced against the anchor at a distancefrom the cylinder head.
 11. The internal combustion engine according toclaim 9, wherein the second spring is braced against a spring seat thatis held by a screw device by which an adjustment of the actuatingmechanism can be conducted.
 12. The internal combustion engine accordingto claim 1, wherein a sensor for detecting anchor positions is providedon one end of the actuating mechanism.
 13. The internal combustionengine according to claim 1, wherein the electromagnet includes at leastone coil core with one or more pole surfaces.
 14. The internalcombustion engine according to claim 1, wherein the two movable anchorshave different dimensions.
 15. The internal combustion engine accordingto claim 1, wherein an oil supply tube terminates in the upper part ofthe actuating mechanism through which lubrication can be obtained usingdrop-by-drop oil provision.
 16. The internal combustion engine accordingto claim 4, wherein the anchor shaft is mounted in the electromagnet.17. The internal combustion engine according to claim 2, wherein asensor for detecting anchor positions is provided on one end of theactuating mechanism.
 18. The internal combustion engine according toclaim 2, wherein the electromagnet includes at least one coil core withone or more pole surfaces.
 19. The internal combustion engine accordingto claim 2, wherein the two movable anchors have different dimensions.